1. Field of the Invention
The present invention relates to a high-hardness amorphous alloy and a high-hardness tool using the same or an amorphous alloy having soft magnetism, and particularly to an amorphous alloy which has a wide overcooled liquid region and which can be obtained in a thick shape.
2. Description of the Related Art
Some of conventional multi-element alloys are known as amorphous alloys (glassy alloys) having a wide supercooled liquid temperature region before recrystallization. This type of amorphous alloy is also known to be formed a bulk shape thicker than an amorphous alloy ribbon produced by a conventional known melt quenching method.
Conventional known amorphous alloy ribbons include ribbons of Fe--P--C amorphous alloys produced in the 1960s, (Fe,Co,Ni)--P--B system and (Fe,Co,Ni)--Si--B system alloys produced in the 1970s, (Fe,Co,Ni)--M(Zr,Hf,Nb) system alloys produced in the 1980s, and (Fe,Co,Ni)--M(Zr,Hf,Nb)--B system alloys. All these alloy ribbons must be produced by quenching at a cooling rate at the level of 10.sup.5.degree. C./S, and the produced ribbons have a thickness of 50 .mu.m or less.
However, all of these conventional known amorphous alloys have no magnetism at room temperature, and when these alloys are considered as magnetic materials, there is a large industrial limit from this point of view. Also the amorphous alloys do not have sufficient hardness, and are thus insufficient for practical use.
Therefore, research and development have conventionally progressed for amorphous alloys which have magnetism at room temperature and which can be obtained in a thick bulk shape.
Although alloys having various compositions exhibit a supercooled liquid region, the temperature width .DELTA.Tx of the supercooled liquid region, i.e., the difference between the crystallization temperature (Tx) and the glass transition temperature (Tg), i.e., the value of (Tx-Tg), is generally small, and these alloys have the low ability to form an amorphous phase and are thus impractical. Considering this property, alloys which have a wide supercooled liquid region, and which can form amorphous alloys by cooling can overcome the limit to the thickness of a conventional known amorphous alloy ribbon, and thus should attract much attention from a metallurgical stand point. However, whether such alloys can be developed as industrial materials depends upon discovery of an amorphous alloy exhibiting ferromagnetism at room temperature.
As amorphous alloys having magnetism, Fe--Si--B system alloys are conventionally known. This system of amorphous alloy has a high saturation magnetic flux density, but has problems in which magnetostriction is at the level of as high as 1.times.10.sup.-5, sufficient soft magnetic characteristics cannot be obtained, heat resistance is low, electric resistance is low, and an eddy-current loss is large when the alloy is used as a core material for a transformer. On the other hand, Co-based amorphous alloys have excellent soft magnetic characteristics, but have problems in which heat stability is poor, electric resistance is not sufficiently high, and thus an eddy-current loss is large when the alloys are used as core materials for transformers. In addition, in the Fe--Si--B system and Co-based amorphous alloys, a amorphous phase can be formed only under the conditions of quenching from a melt, as described above. The formation of a bulk solid thus requires this system of alloy to be passed through the step of grinding the ribbon obtained by quenching a melt and sintering under pressure, thereby causing the problems of requiring a large number of steps and embrittling moldings.
On the other hand, a high-hardness tool comprising a base material and a high-hardness thin film of a carbide, a nitride, a boride or diamond, which is formed thereon, is frequently used. Although the iron group alloys, Mo, ceramics, cemented carbides, cermet and the like are conventionally used as the base material, these materials are unsatisfactory in point of any one of hardness, toughness, and adhesion between the base material and the high hardness thin film, and a base material having further excellent properties is required for a high-hardness tool.